Hydrohalogenation of vinylacetylene



Nov. 19, 1940. A. s. CARTER Erm. l 221,941

HYDROHALOGENATION 0F VINYLACETYLENE Filed July 8, 1957 Rea/dion Pro duc/'J' l bmp/ing' COC/f l 9 Reaczon fon/er 60,0 el? Pac/fea Re ucllon ovwer frederic/f Dowm'zg INVENTUM' ATTORNEY.vl

- Patented Nev. `19, 1940 UNITED -sril'rss OFFICE I l 2,221,941 mnonALocsNanoN or Albert S. Carter, Wilmington, Del., and Frederick B. Downing, Carneys Point, N. J., assignors to E. I. d u Pont de Nemours & Company, Wilmington, Del., a corporation oi Delaware c Application July s, 1932, serial No. 152,518 s 2 claims. .(ol. 26o-sts) This invention relates to the process of hydrohalogenation of unsaturated hydrocarbons and- Simultaneously, a secondary-reaction takes place Carter, Downing and Hutton (U. ,6. Pat. No. 1,950,434) have described one continuous process for carrying out these reactions to control the ratio of products and give a maximum yield oi' lthe mono-chloro compound'ii desired. In this patent, gaseous vinylacetylene is passed over one or -a succession of aqueous solutions of hydrogen chloride in. the presence of a catalyst, .a part of the vlnylacetylene is converted and the reaction products are carried out in the excess unreacted It is an `obiect of this invention to nd an improved method of reacting vinylacetylene with a 3 hydrogen halide of the group consisting of hydrogen chloride and hydrogen bromide. It is a further obiect to nd a continuous method of reacting vinylacetylene with a hydrogen halide of the group consisting of hydrogen chloride and hydrou gen bromide, wherein rapid degeneration oi the catalyst is avoided. A- still further Objectis a continuous process for making,,2chlorol,3

butadiene which may be carried on emciently for,

longer periods of time than 'the processes of the prior,art. Other objects will appear'hereinaiter. These objects have been accomplished by the discovery that bycirculating the solution containing a hydrogen halide oi the groupl consistin g o f hydrogen chloride and hydrogen bromide s and a catalyst, as well as circulating the vinylacetylene, the composition of such solution-may be uniformly controlled andthe continuous process may be carried on eillciently for longer periods o! time. The products may be more easily re- 5o moved and the cost of the apparatus may be materially reduced. For the sake of brevity, Athe process will be hereinafter described with .relation that the process is applicable .using hydrogen bromide in place of hydrogen chloride.

The ligure is a diagrammatic illustration .of a suitable set-up for carrying out the process.

The apparatus for carrying out the process may 5 y be of any suitable design. By way ofexample, a preferred set-up is illustrated in the gure. The reaction is carried out in tower I which is maintained at a constant temperature by a suitable means, such as water jacket 2.' This ytower may lo be packed with copper or glass Irings, carborun-j.

dum, chain or other material suitable-for-pack ing in distillation columns which will withstand the corrosive action of' hydrochloric: acid. V'll'he aqueous solution containingv hydrogen chloride 16 and a catalyst is sprayed into the top of the tower at. 3, ilows down over the packing,l leaves the column through a line, 4, at.. the bottom, and ilows into a trap, 5A, which has a cock, 6, to permit removal of accumulatedchloro-butadiene and tar. 20- Hydrogen chloride gas A:Introduced into the aqueous solution at 'I toc'ompensateior that removed in the tower. Following the introduction of hydrogen chloride, the aqueous `solution iows topump, 8, by means oi which .it is forced through column 9, and preheater, II back to 3.v Column' 9 is packed with copper turnings. `A cock .is supplied at I0 from which samples may be removed to determine thev acidity and control the addition of hydrogen lchloride at 'I. Preheater,'I.I,'brings so the catalyst to the temperature of reaction tower I. Counter to the direction of flow of the aqueous solution, vinylacetylene enters the reaction tower l,at I2 and the unreacted gas together with the I Vproducts of thereaction leave the tower at I3.

-Exllisrtii p A column reactor, having a diameter equal to 36.5% of its length was packed with copper chain. While the temperature was held constantly at C., the ow of aqueoussolution containing '50 hydrogen chloride and catalyst was ilxed at such a speed that the entire solutionjwas circulated through the reactor every twenty seconds, and the volume of the solution was vequal-approximately to ofthe volumeof the unpacked.

reactor. 'I'he solution consisted of 19.5% HC1,` 10% CusClz and 70.5% H2O. This mixture was pumpedrpreheated and vthe HC1 content maintained as previously described. Vinylacetylene y 5 was passed through the reactor at a gas velocity percentages being by weight. In the discussion v and claims where cuprous chloride is specified, it is assumed that the'molecular formula of cuprous chloride is CuaCla with a molecular weight of 198.1, and the proportions of materials have been given on'this basis. Ammonium chloride may also be added in a quantity up to '7.5% 'of the solution, but not in excess of 25% of the cuprous chloride. Metallic copper may be added to maintain the copper of the copper salt reduced to the cuprous state. Howeveninstead of adding metallic copper to the circulating solution, it is preferred to add copper turnngs, wire or even bar copperto the packing in the reactor, or to place -the copper in a separate column through which the aqueous solution flows, and simply pass the solution over the metal during a portion of each cycle.

It has been stated above that the gas is carried through'the reactor in a counter direction to the ow of aqueous solution containing hydrogen 40 chloride and catalyst. For mechanical reasons,

point between 10 and 100 C.v The range from 40 to 65 C. is especially effective, and hence preferred. Pressure assists in .obtaining rapid absorption of vinylacetylene but increases the diiculty of removing the reaction products.

Therefore it is preferred to operate between 600 and 1000 mm. pressure (absolute) though the advantage is recognized of higher production per unit of equipment if operated at higher pressure and with somewhat decreased chemical emciency.

It is preferred to replace the hydrochloric acid consumed in the reaction by introducing gaseous hydrogen chloride into the spent catalyst stream during the recycling process.

The optimum velocity for gas and aqueous solution through the reaction zone is a function of the size and shape of the reaction vessel, the typ'e of packing used therein, the concentration of hydrogen chloride and catalyst in the aqueous solution and other features such as cos't of heating and desired composition of eiiluent gases.

In order to obtain high yields of 2chloro-1,3

'I5 butadiene, the circulation rate of vinylacetylene must be sufficiently high to sweep out practically c CHa-Q(Cl) =CH-CHz(Cl) The circulation rate of vinylacetylene may, of

course, be considerably in excess of this necessary minimum, if desired for 'any reason, `without materially affecting the process, butan excessively high circulation rate is thermally inefficient and results in difllcult problems of condensation and fractionation.

To establish the optimum ow rate for a given apparatus ofthe packed tower type, the aqueous solution may be first circulated until iiooding bccurs. The rate is then slowly reduced until iiooding ceases, thereby establishing a ow which maintains a thin layer of solution over the column packing, presenting a large surface area of solution per unit` volume. The vinylacetylene may then be passed into the reaction chamber at about three times the rate of the aqueous solution. The eilluent gas, comprising a mixture of unreacted vinylacetylene and reaction products, may then be analyzed and the flow of vinylacetylene adjusted until a subsequent analysis of the efiiuent gas shows that the desired reactionrate has been y established. In general, it will be found that this reaction rate will correspond to a contact time of from 5 to 20 seconds, although the time in some cases may be beyond these limits. While the preferred mode of operationcontemplates a solution flow rate less than that necessary to flood the reaction tower, nevertheless, the process is operative with a flooded tower and such operating conditions are within the scope of the invention.

As previously described, the quantity of materials converted to dichlorobutene increases with reaction time, (decrease in gas flow). The increase of reaction product -is roughly proportional to the contact time. Thus, for example, with a set of operating conditions somewhat different from those setforth in the detailed example, the following conversions were obtained:

Among many important features of this invention, two outstanding facts are emphasized. First,- the equipment is of such a nature that it may be constructed of stoneware or costly alloy metals whereas the previous equipment required large moving parts which were constructed of metals for strength and such metals as copper and copper alloys to avoid excessive cost, but

which were not free from serious corrosion.

Second, whereas the old methods gave approximately 100 gms. of chloro-butadiene per kg. of

aqueous solution of hydrogen chloride and catasoV . TABLE 2-chloro-L3-butadiene production at 50 C'.

n Percent conversion to- Relative gas velocity Ohloro- Dlchlorol butadiene butene iyst, this improved method produces approximate- 1y twice as much chloro-butadiene per unit weight of solution with the same yield of addition products. Based on the theory that the reaction takes place in the liquid phase by slight solubility of the y vinylacetylene, this 'improvement is attributed to the fact that the herein described process provides a greater opportunity for the vinylacetylene to dissolve and a greater opportunity for the chloro-butadiene to leave the solution, and hence provides more rapid equilibrium between inlet gas and solution and between solution andvent gas. It is apparent that many widely different embodiments of this invention may bemade Without departing from the spirit and scope thereof, and, therefore, it is not intended to lbe limited except as indicated in the appended claims.

. We claim.:

1. The process of reacting vinylacetylene with hydrogen chloride, which comprises circulating Y and recirculating an aqueous solution containing hydrogen chloride, cuprous chloride and ammonium chloride through a reaction zone maintained at a temperature of between 40 and 65 C., so distributing the solution in the reaction zone as to expose a large surface area per unit volume,l

treating the solution which leaves the reaction zone to remove tar, replenishing the hydrogen chloride content of the solution, passing it over metallic copper and preheating the solution before recirculating it `through the reaction'v zone, passing an excess of vinylacetylene throughthe reaction zone counter-current to the solution at such a rate as to sweep the reaction products away with unreacted vinyiacetylene before the formation of substantial amounts of products other 2. The process of reacting vinylacetylene with hydrogen chloride, which comprises circulating and recirculating an aqueous solution'containing, by weight, 15 to 38% hydrogen chloride, 5 to 25% cuprous chloride and 0 to 7.5% ammonium chloride, the amountl of ammonium chloride being .limited to a `maximum of 25% of the amount of cuprous chloride, through a reaction zone maintained at a temperature Vof between 40 and 65 C., so distributing the solution in the reaction zone as to expose a large surface area of solution per unit volume, treatingy the solution which leaves the reaction zone to remove tar, replenishing the hydrogen chloride content of the solution, passing it over metallic copper and preheating the solution before recirculating it through theV reaction zone, passing an excess of vinylacetylene through the reaction zone counter-current to the `solution at such a rate as to sweep the reaction products away with unreacted vinylacetylene before the formation of substantial amounts of products other than 2chloro-1,3butadiene, separating the unreacted vinylacetylene from the reaction products and returning it to the reaction zone, the

ALBERT VS. CARTER. FREDERICK B. DOWNING. 

